The "include-docstrings" option doesn't work

After cloning the latest Mypy version available on GitHub, I see the "include-docstrings" option available, but running stubgen on an extension module that provides docstrings results in no docstrings at all.

To Reproduce

git clone https://github.com/python/mypy.git

python -m build
python -m pip install mypy-1.7.0+dev-py3-none-any.whl

stubgen --include-docstrings -p myextmodule[.pyd]

python -m mypy.stubgen --include-docstrings -p myextmodule[.pyd]

Expected Behavior

The .pyi file generated from stubgen should contain docstrings declared in the extension module, for classes and functions.

Actual Behavior

There is no docstrings at all, but they exist in the extension module. I have confirmed using help(myextmodule).

Your Environment

python 3.11 for Windows x64
myextmodule installed onto site-packages

• Mypy version used: 1.7.0+dev
• Mypy command-line flags: --include-docstrings -p myextmodule
• Mypy configuration options from mypy.ini (and other config files):
• Python version used: cp3.11

I know this is a new feature, but it seems not to work out.

Start with the stubgen entry points used by stubgen --include-docstrings and python -m mypy.stubgen, then reproduce the behavior against an extension module on Python 3.11. Trace how the option handles classes and functions, and verify that the generated .pyi includes their existing docstrings.